Multi-position character display panel having display cathodes and auxiliary cathodes and circuits for operating the same

ABSTRACT

The display panel is gas-filled and includes a base plate on which a plurality of groups of display cathodes and their conductors are formed, each group of display cathodes being operable to display a character. The panel also includes anode electrodes, one associated with each group of cathodes. The base plate and face plate are spaced apart a small, critical distance and are hermetically sealed together. The panel also includes an auxiliary cathode electrode for each group of display cathodes, the auxiliary cathode electrodes being operable either as sources of electrons for each group of display cathodes to facilitate the operation thereof, or as voltage-regulating elements in the circuit used for driving the panel.

United States Patent 1 Lee MULTI-POSITION CHARACTER DISPLAY PANEL HAVING DISPLAY CATHODES AND AUXILIARY CATHODES AND CIRCUITS FOR OPERATING THE SAME lnventor: James Y. Lee, New Brunswick, NJ.

Assignee: Burroughs Corporation, Detroit,

Mich.

Filed: June 20, 1974 Appl. No; 481,172

References Cited UNITED STATES PATENTS 9/1972 Holz 340/336 12/1973 Harvey 315/169 TV 2/1974 Doanc ct al, 340/336 4/1974 Lee 315/169 TV Into Process June 24, 1975 5/1974 Eisenberg et al 315/169 TV 6/1974 Holz 315/169 R 1 5 7] ABSTRACT The display panel is gas-filled and includes a base plate on which a plurality of groups of display cathodes and their conductors are formed, each group of display cathodes being operable to display a character. The panel also includes anode electrodes. one associ ated with each group of cathodes. The base plate and face plate are spaced apart a small, critical distance and are hermetically sealed together. The panel also includes an auxiliary cathode electrode for each group of display cathodes, the auxiliary cathode electrodes being operable either as sources of electrons for each group of display cathodes to facilitate the operation thereof, or as voltage-regulating elements in the circuit used for driving the panel.

10 Claims, 4 Drawing Figures PATENTEB Jun 2 4 I975 SHEET 1 S83 JUN 24 I975 PATENTEU SHEET 3 An ode1 mi Anode 2- Anode 3 Current H J in Bus 133 Fig.4

MULTI-POSITION CHARACTER DISPLAY PANEL HAVING DISPLAY CATI-IODES AND AUXILIARY CATHODES AND CIRCUITS FOR OPERATING THE SAME BACKGROUND OF THE INVENTION The present invention relates to panel-type segment display devices which include a plurality of groups of cathode electrodes, the cathode electrodes comprising elongated bars or segments arrayed in a pattern so that the cathodes of each group can be selectively energized to display a character. For reasons of economy, the same corresponding cathode electrodes in each group have a common conductor, but the anodes are separately energizable and the panel is operated in a multiplex mode of operation.

In this mode of operation, information signals are applied to all of the cathode electrodes continually, and the anodes are pulsed into operation sequentially. Thus, at any instant, as an anode is energized, the appropriate corresponding information is applied to the associated cathodes which are turned on and display a character. This type of operation is carried out continuously throughout the panel at such a rate that stationary but changeable characters are displayed therein.

While panels of this type operate quite satisfactorily, under some circumstances, as the anodes are operated sequentially, all of the associated cathodes may not turn on. The reason for this failure in cathode operation is not completely understood.

SUMMARY OF THE INVENTION Briefly, a multiple position display panel embodying the invention includes a plurality of groups of cathode electrodes, each representing a character position, and an associated anode electrode. To insure tum-on of the cathodes at each position, an auxiliary gas cell is provided in operative relation with each character position to supply excited particles to facilitate cathode tum-on, and to provide, in a loop circuit, operating bias potential for the associated cathode electrodes.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective exploded view of a display panel embodying the invention;

FIG. 2 is a schematic representation of the panel in FIG. 1 and a circuit in which it may be operated;

FIG. 3 shows curves of anode voltage and the associated current pulses through one of the other electrodes of the panel of FIG. 1 when operated in the circuit of FIG. 2; and

FIG. 4 is a schematic representation of a modification of a portion of the circuit of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The principles of the invention are applicable to a gas-filled display panel of the type known as a PANA- PLEX panel and sold commercially by Burroughs Corporations. This type of panel is a thin, flat, sheet-like member which includes an insulating base plate 20 of glass, ceramic, or the like, and an insulating face plate 24 of glass or the like hermetically sealed together with a small spacing between them provided by an insulating spacer frame 26. The base plate carries, on its top surface, a plurality of conductive leads or runs 30, and a thin layer 40 of insulating material such as glass or eeramic is provided on the conductive runs 30. The layer 40 is provided with a plurality of groups of apertures 50, each aperture exposing one of the runs 30.

Panel 10 includes a group of display cathode electrodes 60 for each group of apertures 50. The cathodes 60A to 60G are used to represent numerals and are generally elongated bars or segments arrayed in a figure 8" pattern, as is well known in the art. Normally, cathodes are also provided to represent decimal points and commas; however, these are omitted to simplify the drawing. Each cathode 60 makes contact with a conductive run 30, with the corresponding cathodes in each group making contact with the same run.

According to the invention, the panel 10 is also provided with an auxiliary cathode 68 at each character position, and each such auxiliary cathode comprises a generally triangular or elongated member disposed adjacent to the lower or upper margin of each group of display cathodes and connected through an aperture in layer 40 to a conductive run 30 on the base plate.

Under some circumstances, it may be desirable to provide a second layer of insulating material 64 having a plurality of apertures 66, each enclosing one of the cathode electrodes. Such an arrangement is shown in copending application Ser. No. 446,832, filed Feb. 28, 1974.

All of the panel elements which are supported on the base plate 20 may be formed by a screen-printing process.

Panel 10 includes an anode electrode 90 for each group of display cathode electrodes 60 and auxiliary cathode 68. The anode electrodes 90, in one arrangement, comprise thin, transparent conductive films of gold, tin oxide, or the like formed on the inner surface 96 of the panel face plate 24 and overlaying the cathodes with which they operate.

The panel includes means for shielding the auxiliary electrodes 68 from view through face plate 24, and one such means comprises a layer 100 of opaque material formed on the inner surface 96 of face plate 24 between the anodes 90 and the face plate. Any one suitable shield means may also be provided.

The panel 10 also preferably includes a keep-alive cell (not shown) positioned at the left-hand or righthand end of the panel, depending on the direction in which the panel is scanned. The keep-alive cell usually comprises small-area cathode and anode electrodes formed on the insulating layer 40.

The panel 10 is filled with the desired gas atomsphere such as neon, argon, xenon, etc., singly or in combination, along with a vapor of a metal such as mercury included in the gas to minimize cathode sputtering. A wide range of gas pressures may be used, for example, from about 20 to about 350 Torr, or more, at ambient temperature, with a pressure selected from the range of about to about I25 Torr at room temperature being commonly and conveniently used.

Any suitable arrangement may be used to make electrical connection to the anodes and to the cathodes through their runs 30. One such arrangement is shown and described in copending application Ser. No. 370,786, filed June 18, I973.

The display panel 10 and a circuit in which it may be operated are shown schematically in FIG. 2. In the circuit, the anode electrodes are each connected through a diode 113 to a first bus 112 which is connected to a positive DC. power source VI. Each anode is also connected to an anode driver 116 for energizing each anode sequentially. Each cathode conductor 30 is connected through a diode H8, oriented as shown, to a second bus 120, known as a cathode restoring bus, and through a capacitor 122 and a resistor 124, in series, to a third bus 126 which is connected in turn to a negative DC. power supply V2 of the order of 40 volts. The junction 127 of each capacitor 122 and resistor 124 is also connected to a cathode driver 13] for applying information signals to the cathode leads 30 and the associated cathodes 60. The circuit includes a source 128 of information signals coupled to signal processing circuitry 129 including, for example, a computer, encoders, decoders, character generator, and the like, as is well known in the art. Circuit 129 has an output lead 114 to each cathode driver. Also provided are synchronizing circuits 130 for operating each of the anodes sequentially and simultaneously applying information signals on leads 114 to the cathode drivers, as is well known in the art.

According to the invention, the common conductor 30 connected to each of the auxiliary cathodes 68 is connected by lead 133 to the base of a PNP transistor 137, the emitter of which is connected through a relatively large resistor 141 to a negative DC. power source V3 of the order of-l 50 volts to l 80 volts. Resistor 141 is sufficiently large to constitute the cathode current-determining element of the circuit. The emitter of transistor 137 is also connected through a resistor [45 to its base electrode, and its collector is connected through a Zener diode 160, oriented as shown, to the base of a PNP transistor 170. The collector of transistor 170 is connected through a resistor 175 to the power supply V3, and its emitter is connected both to bus 120 and through a capacitor 177 to ground.

In operation of the invention, in general terms, each of the anode electrodes 90 is energized separately and in turn, and simultaneously, information signals are applied to the cathode drivers 13! and thus to the display cathodes 60 so that, as each anode is energized, selected display cathodes are energized and a character is displayed. In this operation of panel 10, the auxiliary cathode electrodes 68 serve to set the display cathodes 60 to the required operating bias level as follows.

When the system is turned on, the anodes begin to scan, and information signals are applied to the cathode drivers; however, the display cathodes 60 do not turn on because the cathode bus 120 is held at ground potential by capacitor 177. The auxiliary cathodes see the power supply V3, and at some panel position, determined randomly by circuit and panel parameters, the auxiliary cathode 68 exhibits cathode glow, and current flows between it and its anode 90. This current flows from source V3 through resistors 14] and 145, and this causes transistor 137 to turn on and conduct current through its emitter collector path. This current flow produces a voltage drop across diode I60 and drives the base of transistor 170 in a generally negative direction, and current flows through its emitter collector path. This causes capacitor 177 to charge negatively until a potential is reached which is more positive than that on auxiliary electrode 68. Diode 160 determines this potential which appears on bus 120 and comprises the proper hold-off bias for the cathode segments 60. This potential is just sufficient to prevent these display cathodes from glowing until selected cathode drivers are energized and negative potentials are applied to the associated selected display cathodes. The negative potentials, coupled with the applied bias, are sufficient to cause the selected cathodes to exhibit cathode glow.

With the cathode electrodes thus biased, information signals of minimal magnitude can be used to cause cathode glow. Typically, in panels of the type known as PANAPLEX panels, such signals may be about 25 to 50 volts in amplitude.

As the panel 10 operates each position in turn, as each anode is energized, its associated auxiliary cathode 68 performs the biasing operating described above before its associated display cathodes, selected by the input information signals, exhibit cathode glow.

FIG. 3 shows voltage pulses applied to three anodes sequentially with the accompanying current pulse which passes through the auxiliary electrode circuit as each anode is energized.

In a modification of the invention illustrated in FIG. 4, the resistor 14! of FIG. 2 is replaced by an NPN transistor 191 connected as a constant current source with its collector connected to the emitter of transistor 137, its emitter connected through a resistor 193 to voltage supply V3, and its base connected both through a Zener diode 195 to the voltage supply V3 and through a series resistor 197 and capacitor 199 to the collector of transistor 137 and thus to the anode of diode 160. The junction 201 of the resistor 197 and capacitor 199 is connected to a source of reference potential such as ground.

In the modification of FIG. 4, transistor 191 represents a constant current source which provides improved regulation and control of the current flow through the auxiliary electrodes independently of variations in the system power supply.

In one circuit used for operating a PANAPLEX panel of the type manufactured and sold by Burroughs Corporation, the following circuit parameters were used:

Resistor 124 27,000 ohms Resistor [45 5,000 ohms Resistor [41 200,000 ohms Resistor I L000 ohms Capacitor I22 .01 uf Capacitor 177 1.0 uf Transistor 170 2N4888 Transistor 137 2N5 551 V3 l volts VI and V2 20 volts Diode I60 [M4627 What is claimed is:

l. A display panel and system for operating the same comprising a gas-filled envelope including a base plate and a face plate having a viewing window,

a plurality of groups of display cathode electrodes supported on said base plate and adapted to be operated in different combinations to display different characters,

corresponding cathodes in all of the groups being interconnected by a single common conductor, there thus being a single common conductor for each corresponding cathode electrode in each of said groups,

an auxiliary cathode electrode associated with each said group of display cathodes,

an auxiliary common conductor connected to all of said auxiliary cathodes,

an anode electrode associated with each said group of cathodes,

means coupled to said anodes and said common conductors for sequentially energizing each of said anode electrodes and simultaneously applying information signals to selected ones of said common conductors and their associated display cathodes, and

a circuit loop connected between said auxiliary common conductor and all of said single common conductors including means for generating a bias volt age in response to current flow through an auxiliary electrode and applying said bias voltage to all of said display cathodes.

2. The system defined in claim 1 wherein said circuit loop includes a diode for generating said bias voltage.

3. The system defined in claim 1 wherein said loop includes a current flow path through a resistive Path to a source of negative DC. potential, and a plurality of semiconductor devices coupled between said path and said common conductors, said semiconductor devices operating to couple said bias voltage to said common conductors.

4. The system defined in claim 1 wherein all of said common conductors are connected to a common bus, and said common bus is coupled through a capacitor to ground.

5. The system defined in claim 3 wherein said plurality of semiconductor devices includes a first semiconductor device coupled through a diode and a second semiconductor device to all of said common conductors.

6. The system defined in claim 5 wherein said diode is a Zener diode.

7. A system for operating a multiple position display device having a plurality of groups of display cathode electrodes and an anode electrode associated with each said group, corresponding cathodes in the different groups being interconnected by a single common conductor, there thus being a single common conductor for each corresponding cathode electrode in each of said groups, there being an auxiliary cathode electrode associated with each group of cathode electrodes and auxiliary common conductor interconnecting all of said auxiliary cathode electrodes, said system including an anode driver circuit connected to each of said anode electrodes,

a cathode driver connected to each of said common conductors for applying display signals thereto,

a bus coupled to all of said common conductors connected to said display cathode electrodes, and

a current flow path from each anode through said auxiliary common conductor including means for developing a voltage proportional to current flow therein and for applying said voltage to said bus,

said voltage biasing all of said display cathodes at a level such that said display signals, when applied to selected cathode drivers, can cause such cathode drivers to energize the associated display cathodes to exhibit cathode glow.

8. The system defined in claim 7 and including :1 capacitor coupling said bus to ground.

9. The system defined in claim 7 wherein said current flow path includes a first semiconductor device coupled through a diode and a second semiconductor device to said bus.

10. The system defined in claim 7 wherein said current flow path extends from said auxiliary common conductor through a resistor to a power supply, and it includes a first transistor having its base connected to said path, its emitter connected through said resistor to said power supply, and its collector connected through a Zener diode to the base of a second transistor which has its emitter connected both to said bus and through a capacitor to ground, and has its collector connected through a resistor to said power supply. 

1. A display panel and system for operating the same comprising a gas-filled envelope including a base plate and a face plate having a viewing window, a plurality of groups of display cathode electrodes supported on said base plate and adapted to be operated in different combinations to display different characters, corresponding cathodes in all of the groups being interconnected by a single common conductor, there thus being a single common conductor for each corresponding cathode electrode in each of said groups, an auxiliary cathode electrode associated with each said group of display cathodes, an auxiliary common conductor connected to all of said auxiliary cathodes, an anode electrode associated with each said group of cathodes, means coupled to said anodes and said common conductors for sequentially energizing each of said anode electrodes and simultaneously applying information signals to selected ones of said common conductors and their associated display cathodes, and a circuit loop connected between said auxiliary common conductor and all of said single common conductors including means for generating a bias voltage in response to current flow through an auxiliary electrode and applying said bias voltage to all of said display cathodes.
 2. The system defined in claim 1 wherein said circuit loop includes a diode for generating said bias voltage.
 3. The system defined in claim 1 wherein said loop includes a current flow path through a resistive path to a source of negative D.C. potential, and a plurality of semiconductor devices coupled between said path and said common conductors, said semiconductor devices operating to couple said bias voltage to said common conductors.
 4. The system defined in claim 1 wherein all of said common conductors are connected to a common bus, and said common bus is coupled through a capacitor to ground.
 5. The system defined in claim 3 wherein said plurality of semiconductor devices includes a first semiconductor device coupled through a diode and a second semiconductor device to all of said common conductors.
 6. The system defined in claim 5 wherein said diode is a Zener diode.
 7. A syStem for operating a multiple position display device having a plurality of groups of display cathode electrodes and an anode electrode associated with each said group, corresponding cathodes in the different groups being interconnected by a single common conductor, there thus being a single common conductor for each corresponding cathode electrode in each of said groups, there being an auxiliary cathode electrode associated with each group of cathode electrodes and auxiliary common conductor interconnecting all of said auxiliary cathode electrodes, said system including an anode driver circuit connected to each of said anode electrodes, a cathode driver connected to each of said common conductors for applying display signals thereto, a bus coupled to all of said common conductors connected to said display cathode electrodes, and a current flow path from each anode through said auxiliary common conductor including means for developing a voltage proportional to current flow therein and for applying said voltage to said bus, said voltage biasing all of said display cathodes at a level such that said display signals, when applied to selected cathode drivers, can cause such cathode drivers to energize the associated display cathodes to exhibit cathode glow.
 8. The system defined in claim 7 and including a capacitor coupling said bus to ground.
 9. The system defined in claim 7 wherein said current flow path includes a first semiconductor device coupled through a diode and a second semiconductor device to said bus.
 10. The system defined in claim 7 wherein said current flow path extends from said auxiliary common conductor through a resistor to a power supply, and it includes a first transistor having its base connected to said path, its emitter connected through said resistor to said power supply, and its collector connected through a Zener diode to the base of a second transistor which has its emitter connected both to said bus and through a capacitor to ground, and has its collector connected through a resistor to said power supply. 